Humans – and not rats – could have been the cause for the spread of plague during the Black Death, a new study suggests.

The Black Death was one of the worst pandemics in human history. It devastated European populations from 1346 to 1353 and resulted in the deaths of an estimated 75 to 200 million people.

It has long been thought that the plague, caused by the bacterium Yersinia pestis, which lasted in Europe until the early 19th century, was spread by rats.

But now scientists from the University of Oslo and the University of Ferrara believe human “ectoparasites”, such as body lice and human fleas, might be more likely to have caused the epidemic.

Rats eradication

Using mortality data from nine plague outbreaks in Europe between the 14th and 19th centuries, the teams tracked how the plague developed.

They created models of how a disease could be spread by rats, airborne transmission, and fleas and lice on humans and clothes.

They found that, in seven of the cases, there was a closer resemblance between the human model and the outbreak when compared with the other two alternatives.

In the paper, published in the Proceedings of the National Academy of Science, the researchers said: “While it is commonly assumed that rats and their fleas spread plague during the Second Pandemic, there is little historical and archaeological support for such a claim.

“Here, we show that human ectoparasites, like body lice and human fleas, might be more likely than rats to have caused the rapidly developing epidemics in pre-Industrial Europe.”